This invention relates to surgical instruments for penetrating or dissecting bodily tissue. More specifically, it relates to penetrating instruments which incorporate an imaging element for viewing. These instruments allow access into a body cavity when the instrument is advanced into the tissue, and simultaneously provide the ability to visualize the penetrated tissue during the advancement.
One of the key surgical activities which is required during every surgical procedure is the creation of an access opening into the body cavity at the desired surgical site. For many years, the surgeon created the access opening by simply making a large incision through the body wall to expose the body cavity. The length of the incision would depend on the size of conventional surgical instruments and the ability of the surgeon to properly and efficiently use these instruments within the body cavity through the incision created. Once the surgeon finished the surgical procedure, the incision could be fastened using known techniques. Unfortunately, due to the nature of these conventional, open surgical procedures, long incisions were often necessary. Open surgery can therefore be traumatic to the patient because, among other things, the recuperative period required to fully heal from the effects of the large incision may be significant.
Since a patient's recuperative period can be significant in connection with conventional open surgery, new surgical procedures and instruments to support those procedures are becoming available. The most popular alternative to open surgery currently is endoscopic surgery. Endoscopic surgery involves the use of a number of small diameter openings providing access into the body cavity. Unlike the large incisions required for open surgery, these small diameter openings readily heal following surgery, and require much less recuperation time for the patient.
The cornerstones which have made endoscopic surgical procedures possible are the miniaturized camera, or endoscope, and the surgical penetration instrument providing the small diameter opening for access into the body cavity, conventionally referred to as the trocar. Since both of these instruments are critical for the performance of endoscopic surgery, each will be discussed briefly below.
An endoscope is an elongated, generally cylindrical imaging and visualization instrument. It can be attached to a light source which provides illumination within the body cavity at the surgical site. The endoscope contains a miniaturized camera lens which is capable of transmitting the illuminated images at the surgical site to the surgeon during a surgical procedure. The endoscope is frequently attached to a video monitor during endoscopic surgery, so that the surgical team can observe the surgical procedure within the body cavity on the video monitor screen. The endoscope has made it possible to indirectly observe the surgical procedure without having the direct access into the body cavity, and consequently the large incisions it requires to create such direct access.
Critical to the success of endoscopic surgery is the creation of a small diameter passageway into the body cavity for subsequent insertion and withdrawal of surgical instruments. These instruments include, for example, an endoscope, and elongated instruments to cut, fasten, coagulate and excise desired tissue. The trocar has become the instrument of choice to create this small diameter passageway. A trocar is a penetrating assembly including a cutting tool, commonly referred to as the trocar obturator. The obturator has an elongated, cylindrical shaft from which extends a penetrating tip to create and enlarge an opening into tissue as the obturator is advanced. The obturator is slidably received in a sleeve, commonly referred to as the trocar cannula. As the obturator is advanced into the tissue, the cannula likewise is advanced. When the obturator has completely punctured the body wall, the obturator is withdrawn from the trocar assembly, leaving behind the trocar cannula. The trocar cannula then provides the passageway into the body cavity through a relatively small diameter opening.
One of the first technical challenges in connection with the design and manufacture of the trocar related to the incorporation of features into the trocar to enhance its safety. Specifically, it was important to develop a safety trocar which could substantially lessen the possibility of unintentional tissue or organ puncture. The seminal patent that describes a mechanism for protecting bodily tissue and organs from inadvertent puncture during advancement of the instrument into the body cavity is U.S. Pat. No. 4,535,773 (Yoon, issued August, 1985). This patent describes a trocar assembly which includes a safety shield interposed between the trocar obturator and cannula. The shield is biased in an extended position to cover the penetrating tip of the obturator. When the surgeon desires to penetrate tissue with the trocar, the safety shield retracts and exposes the penetrating tip when the surgeon applies pressure against the body wall. The shield remains in the retracted position so long as pressure is continuously applied. When the surgeon fully punctures the body wall, the pressure is relieved and the safety shield returns to its extended position covering the penetrating tip. Therefore, inadvertent puncture of bodily tissue and organs within the body cavity can be avoided. Another trocar assembly with a safety shield mechanism is described in U.S. Pat. No. 5,226,426 (Yoon, issued Jul. 13, 1993). This patent describes a trocar obturator in the form of a hollow needle through which the safety shield (or safety "probe"), is disposed. Once again, the safety probe covers the sharp tip of the needle until pressure is applied during insertion.
Since the development of the safety-shielded trocar, other mechanisms for protecting tissues and organs from inadvertent puncture during endoscopic surgery have been developed. For example, mechanisms have been developed where the obturator retracts into the trocar cannula after puncture. These "retractable obturator" trocars may be equipped with a safety shield which simultaneously moves to an extended position as the obturator retracts within the trocar cannula.
While numerous trocar assemblies have been designed to prevent inadvertent puncture, all of these instruments still have one basic problem. Regardless of the safety mechanisms built into these instruments, the surgeon cannot avoid the fact that he is still puncturing tissue blindly. Not only is the puncture performed blindly, but the instruments are expensive to manufacture and occasionally fail in connection with the safety features incorporated to prevent inadvertent puncture during the blind insertion. Therefore, significant new designs for trocar assemblies have been developed.
One of the more remarkable developments in the design of trocar assemblies relates to the incorporation of visualization concurrently with penetration. This has been made possible by the "marriage" of the endoscope for imaging and visualization, and the trocar for penetration to provide the endoscopic access opening. The first patent to describe a surgical penetration instrument adapted for visualization during penetration is U.S. Pat. No. 5,271,380 (Riek, et al., issued Dec. 21, 1993). The Riek patent describes a penetrating instrument including a hollow, cylindrical sleeve and an imaging element attached to the sleeve at its distal end. The imaging element is a transparent, optical "window". In a preferred embodiment, it has a conical configuration to facilitate the advance of the instrument into body tissue. A fiber optic cable extends through the hollow shaft and is positioned adjacent the proximal end of the window. It delivers light from a light source through the optical window into surrounding bodily tissue. A camera lens is also provided in the shaft to deliver illuminated images transmitted through the optical window to the surgeon. When the surgeon advances the instrument into bodily tissue, the surgeon can view the tissue in front of and surrounding the optical window during the penetration. This feature is significant because the surgeon can adjust the path of advancement if he approaches tissue or organs which should not be touched. In this way, the incorporation of a safety shield or another mechanism to protect tissue or organs from inadvertent puncture during a blind insertion is unnecessary.
Although the surgical penetration instrument described in the Riek patent represents a major advance in trocar technology, the clarity of images transmitted to the surgeon of the surrounding tissue during advancement is less than what would be optimally desired. Significantly, the transparent optical window is hollow, and the fiber optic cable delivering light into the surrounding tissue for illumination is spaced from the window surface. Light rays must therefore travel from the cable through the void of the hollow window before contacting the window surface. As light is carried from the fiber optic cable to the surface of the window, a significant proportion of that light will not pass through the window into the surrounding tissue, but rather reflect back into the camera lens. This reflection causes unwanted glare, and prevents optimum clarity during visualization.
In another embodiment, the Riek patent describes a second fiber optic cable for delivering light which extends through the window and is positioned at the tip of the window. While this cable does indeed contact the surface of the window, it only does so at the tip and therefore is unable to provide adequate illumination of the tissue surrounding the entire conical window. In other words, it can only provide illumination of tissue in front of the tip of the window.
Another recently issued patent representing yet another significant advance in the state of the art with respect to surgical penetration instruments providing simultaneous visualization is U.S. Pat. No. 5,334,150 (Kaali, issued Aug. 2, 1994). The Kaali patent also describes an instrument including an elongated hollow shaft to which is attached an imaging element in the preferred form of a transparent conical window. However, instead of extending a fiber optic cable and lens into fixed positions adjacent the proximal end of the transparent window within the hollow shaft, the Kaali patent describes using a fully integrated endoscope which can be inserted through the hollow shaft adjacent the window to provide illumination and visualization of tissue in front of and surrounding the transparent window during insertion. Unfortunately, once again the optical clarity of the surrounding tissue as the instrument is advanced is less than ideal. This is so because the transparent window in the specific embodiments illustrated in this patent are substantially solid. Depending on the material of construction for the window, visual distortion and other undesirable optical effects can occur when light travels through the solid mass of the window,
Another feature which has recently been added to the surgical penetration instruments described in the Riek and Kaali patents is a cutting blade extending outwardly from the transparent optical window to facilitate the advance of the instrument into tissue. Unfortunately, these blades may inadvertently cut unwanted tissues or organs and cause undesirable damage to gaskets and other delicate elements located within the housing of the cannula sleeve when the instrument is removed from the cannula sleeve.
It should now be apparent to the reader that while significant advances have been made in the development of surgical penetrating instruments adapted for simultaneous visualization, there are still certain problems which need to be overcome. For example, what is needed is a surgical penetration instrument which can provide visualization with the optimum degree of clarity. Additionally, such an instrument would desirably incorporate a blade outwardly of the transparent optical window which would not cause unintended trauma to tissue or damage delicate elements in the cannula housing of the instrument, but rather facilitate the advance of the instrument into tissue for ease of penetration.